Process for treating animal skins and hides



Patented Apr. 12, 1938 PATENT OFFICE PROCESS FOR TREATING ANIMAL SKINS HIDES Robert Miiller, Hamburg, Germany No Drawing. Application May 20, 1936, Serial No. 80,712. In Germany June 21, 1933 6 Claims.

The present invention relates to the treatment of animal skins and hides for use in the manufacture of leather.

For the treatment of animal skins and hides several proposals have been made in order to obtain a shorter or longer preservation; a short preservation comes into question when the soaking process is carried out. None of these pro posals results in a satisfactory effect. The effect of the above-mentioned processes was either insufficient insofar as the protection of the skin fibres is concerned, or chemical reactions took place with'the protein substances, whereby difliculties occurred when the skin material was worked up in the leather factories; in some cases impossible. I

It is well known that the salting of the skins and hides-generally used to-day-does not result in a sufficient preservation,.as there are types of bacteria the growth of which is favoured by the salt.

Also the drying of the raw hides is attended by many dlfficlllties; e. g. putrefaction during the drying, blood'putrefaction, bad manufacturing of the leather in the leather factories, and the material becoming horny during the drying.

According to the present invention it has now been found that a good preservation of hides and skins may .be obtained if these materials are treated with hydrocarbons which are insoluble in water but are emulsifiable therein, and which show the following other properties:- I

They must be in the liquid state at the temperature of treatment, and must have no greater evaporation velocity than 10, if acetone is 100, i. e., the time of evaporation must be ten times as long as that of acetone, furthermore they must be free from the'tendency to'resinify,'and innecessity for low evaporation velocity, this must be defined in terms of the volatility of acetone at ordinary temperatures, and for the purpose of the specification the low evaporation velocity may the production of good' quality leather was quite active to protein substances. With regard to the ably such hydrocarbons are used which are not caustic and are not poisonous to the human'subject. These requirements are fulfilled especially be the following group of organic compounds:- hydrocarbons containing only carbon and hydro- 5 gen in the mo}ecule, esters and, preferably, chloroderivatives of the above-mentioned compounds and, more especially, derivatives of the mentioned compounds which contain at least one alcoholic hydroxylgroup (i. e., not a phenolic 10 hydroxyl group). As is generally known, especially such compounds resinify which have several conjugated double linkages. For a short preservation, as necessary in the case of soaking, naturally smaller amounts of the mentioned prod- 15 ducts are necessary than for longer preservations. There is practically no lower limit for the amounts necessary because, as is well known, even traces of hydrocarbons show a bactericidal action. There is also no upper limit for the amounts necessary, but generally it is sufficient, to use 3% to 5%, calculated on the weight of the hides or skins. The hydrocarbons which may be used for the present process belong to the aromatic, hydroaromatic, aliphatic or alicyclic series. The following substances may be mentioned by way of example only:-

Benzene hydrocarbons, naphthene hydrocarbons, terpene hydrocarbons, benzine fenchyl alcohol, benzyl alcohol, cyclohexanol, terpinenol, m-dichlorobenzene, chloronaphthalene and perchlorethane.

Advantageously the above-mentioned products may be used also in admixture.

The process may be carried out atany tem-' perature provided that the products used for treatment according to the invention are neither in the solid nor in the gaseous state at the temperature used, but preferably the process is carried out at normal temperatures. Emulsifiable in connection with the present invention means that the substances used contain an emulsifier.

' The skins and hides thus treated show a far greater resistance against the influence of bacteria than was hitherto known. Furthermore, all the above-mentioned disadvantages connected with the former processes are avoided.

It has already been proposed to use hydrocarbons or their chloro-derlvatlves for de-fatting skins and hides. Apart from the factthat-defatting is something diflerent from preserving, only hydrocarbons have been mentioned showing an evaporation velocity greater than that given as limit for the products of the present invention.

The following examples may be given for the composition of the mixtures used according to the invention; the last mentioned component is always the emulsifier.

may either be coated with the above-mentioned products or be put into an emulsion of these products, or coated with the emulsion;' finally it is pcnsible to mix the products with the preserving salt hitherto used (NaCl) and to salt the hides by means of this mixture.

The following examples illustrate how the invention may be carried out in practice, but it is to be understood that the invention is in no way limited to the details given in these examples:-

Emzmpie 1 100 kilograms of hides are coated on their inner side (i. e., the side away from the hair) with 42 kilograms of the above mixture (1);

they are left during the night and salted the next day in the ordinary way.

Example 2 160 kilograms of hides are coated on their inner side with an emulsion of the products ac cording to the above composition (2) in the fourfold amount of water and then treated in the way described in Example 1.

Example 3 The hides are put into an emulsion of ll) kilogrammes of the products of the above composition (3) in 109 litres of water for 24 hours, and then treated as described in Example 1.

7 Example 4 100 kilograms of salt are mixed with 7 to 10 kilograms of one of the above-mentioned products. The hides and skins are then salted by means of this'salt.

I Example For'disinfecting, 'viz., for the protection of hides while soaking them, there is added to the soak 1 to 1V; kilograms per 1 cubic metre at one of the above-mentioned products.

Apart from the preserving and disinfecting efiect of the mentioned products, there are further advantages obtained by usingthem (for preserving orin soaking) and these advantages are obtained in the leather manufacture thereby that an almost complete uniform swelling of all skin fibres is obtained such as cannot be observed with the use of alkalies or capillary active substances alone or by solvents alone. By this uniform absorption of water, however, the physical state of the individual hide fibres is also apparently equalized; over-stretched fibres contract to corresponding normal lengths; contracted fibres stretch (disappearance of folds) and a homogeneous skin material is obtained which is in all parts equally extensible and elastic.

I In connection therewith the tanners pit may be maintained weaker, the dye-stuffs result more uniform and deeper colours (whereby the amounts of dye-stuffs hitherto used may be reduced for about 20%), the previously used quantity of fat may be reduced for about 25%, the leather becomes smoother and of better appearance, no ribs, especially neck folds, are observed; finally the leathers have from 1,5 to 2% more surface (gain in dimensions or size).

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, 1 declare that what I claim is:-

1. A method of preserving animal skins and hides which method comprises incorporating into the raw unsalted hides water insoluble organic hydrocarbons which are in the llquidstate, emulsified by the action of an emulsifying agent, and

which show at the uttermost an evaporation velocity of one-tenth of that of acetone, no tendency to resinify and are inactive to albuminous substances, and leaving said hydrocarbons in the hides for the preservation period.

2. A method of preserving animal skins and hides which method comprises subjecting the same to the action of water insoluble organic chloroderivatives of hydrocarbons which are in the liquid state, emulsified by the action of an emulsifying agent, and which show at the uttermost an evaporation velocity of one-tenth of that of acetone, no tendency to resinify and are inactive to albuminous substances.

3. A. method of preserving animal skins and hides which method comjnises mbjecting the same to the action of mixtures of water insoluble organic hydrocarbonswithwater insoluble organic chloroderivatives of hydrocarbons which are both in the liquid state, emulsified by the action oi an emulsifying agent and which show at the utterrnost an evaporation velocity of one-tenth of that of acetone, no tendency to resiniiy and are lnac tive to albuminous substances.

4. A method of preserving animal skins and hides which method comprises subjecting the same to the action of -water insoluble organic alcoholic hydroxyl derivatives of hydrocarbons which are in the liquid state, emulsified by the action of an emulsifying agent, and which show at the uttermost an evaporation velocity of onetenth of that of acetone, no tendency to resinify and are inactive to albuminous substances.

5. A method of preserving animal skins and hides which method comprises subjecting the same to the action of .water insoluble organic hydrocarbons in mixture with water insoluble organic alcoholic hydroxyl derivatives of hydrocarbons which are both in the liquid state, emulsifled by the action of an emulsifying agent, and which show at the uttermost an evaporation velocity-of one-tenth of that of acetone, no tendency to resinify and are inactive to albuminous substances.

6. A method of preserving animal skins and hides which method comprises subjecting the same to the action of water insoluble organic hydrocarbons in mixture with water insoluble organic alcoholic hydroxyl derivatives of hydrocarbons and chloroderivatives of hydrocarbons which are all in the liquid state, emulsified by the action of an emulsifying agent, and which show at the uttermost an evaporation velocity of onetenth of that of acetone, no tendency to resinify andare inactive to albuminous substances.

, ROBERT MULLER. 

